1. Field of the Invention
The present invention relates to a navigation apparatus, and more particularly to a navigation apparatus having a display capable of stereo display.
2. Description of Relevant Art
Conventionally, as a display capable of stereo display, a system where two panels are disposed with a given distance to each other so as to display a superimposed image on the line of sight of an observer, and the superimposed image can be visually percepted as a stereo image through observation of images displayed on the two panels, has been developed. This is disclosed in claim 1 of Japanese Laid-Open Patent Publication No. 2004-361465.
In the above display method, two same images are displayed on the two panels respectively so that the two same images are superimposed, and luminance of the images is differentiated according to a depth of the panel. The luminance of a front panel is increased for an object located at a front side, and that of a back panel is increased for an object located at a back side. With the above, an object can be displayed as if it is located at a middle position of two panels.
In addition, there exists a navigation apparatus for displaying a quarter guide map (This is disclosed in, for example, claim 1 of Japanese Laid-Open Patent Publication No. 2001-311625), and an enlarged intersection map (This is disclosed in, for example, claim 1 of Japanese Laid-Open Patent Publication No. H7-332994). These displays are important guide displays for informing a driver of a leading direction and a destination, thereby resulting in requirement of a high visual perceptibility.
In the navigation apparatus, it is necessary to display an elevated road and a road (hereinafter, referred to as non-elevated road) constructed under the elevated road. If a status where the elevated road is overlapped with the non-elevated road in above and below is displayed in a two-dimensional plane, a display of the non-elevated road is hidden by a display of the elevated road. Therefore, it becomes difficult to distinguish whether a car mark showing an own vehicle is on the elevated road or the non-elevated road, as well as the visual perceptibility of the display of the non-elevated road is decreased. Therefore, if a case where the display method described in the Japanese Laid-Open Patent Publication No. 2004-361465 is applied to a display of the elevated road is considered, that is, if the elevated road is displayed on the front panel and the non-elevated road is displayed on the back panel along the line of sight, the elevated road is always displayed on the front panel with high luminance, thereby resulting in difficulty to see the car mark when the own vehicle runs on the non-elevated road under the elevated road. In addition, the display methods of the quarter guide map and enlarged intersection map described in the Japanese Laid-Open Patent Publication Nos. 2001-311625 and H7-332994 have been poor in the visual perceptibility, because the maps and the car mark are displayed together on same display.
It is, therefore, an object of the present invention to improve a visual perceptibility of an elevated road in a planar map display where the elevated road is overlapped with a non-elevated road in above and below.
It is another object of the present invention to improve a visual perceptibility of a leading guide map which is displayed by superimposing the map on a map display.